Die assembly for molding cylindrical body and cylindrical body produced using same

ABSTRACT

A molding die assembly includes an outer molding die which forms an outer peripheral surface of a cylindrical mold, and, an inner molding die which forms an inner peripheral surface of the cylindrical mold, wherein the outer molding die is comprised of a plurality of split die elements which are split at an oblique separating surface inclined with respect to the circumferential and axial directions of the cylindrical mold.

This is a division of application Ser. No. 08/534,403, filed Sep. 27,1995, now U.S. Pat. No. 5,738,855 the contents of which are hereinexpressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a die assembly for molding acylindrical body, such as a movable lens barrel or the like, and alsorelates to the cylindrical body produced by the molding die assembly.

2. Description of Related Art

A cylindrical body, for instance, of which a zoom lens barrel for a zoomlens camera is made, is molded by an injection molding process using adie assembly. In this case, the finished molded product (i.e. thecylindrical body) has a parting line which appears on the outerperipheral surface thereof. In general, this parting line, whichcorresponds to a connecting line between a plurality of split dies,extends in a direction parallel with the optical axis of the lensbarrel.

In the case where the cylindrical body is used for a movable lens barrelhaving a parting line of a certain height extending parallel with theoptical axis, a light intercepting member, which optically interceptslight in a gap between the movable lens barrel and an outer ringprovided on the outer peripheral surface thereof, can be partly deformedor deflected by the parting line, thus resulting in the formation of aclearance between the movable lens barrel and the outer ring. Since theparting line extends in a direction parallel with the optical axis, asmentioned above, the clearance caused by the deformation or deflectionof the light intercepting member continuously extends in the opticalaxis direction. In this state, if light is made incident upon the lensbarrel from the front, the light partly passes through the clearanceinto the lens barrel. This would have an adverse influence on thephotographing efficiency.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a molding dieassembly for producing a cylindrical body, in which light can beintercepted in the gap between the cylindrical body and an outer orinner ring.

Another object of the present invention is to provide a cylindrical bodyin which a gap between the same and an outer or inner ring can beoptically interrupted.

To achieve the object mentioned above, according to an aspect of thepresent invention, there is provided a molding die assembly for moldinga cylindrical article(mold) including an outer molding die which formsan outer peripheral surface of the cylindrical mold and, an innermolding die which forms an inner peripheral surface of the cylindricalmold outer molding die includes a plurality of split die elements whichare split at an oblique separating surface which is inclined withrespect to the circumferential and axial directions of the cylindricalmold.

According to another aspect of the present invention, there is provideda molding die assembly for molding a mold article having an outerperipheral surface including: a plurality of split die elements whichform the outer peripheral surface of the mold; an oblique separatingsurface which is provided with each of the split die elements, and thesplit die elements forming an inner cylindrical shape when they areconnected at the oblique separating surface. The oblique separatingsurface may be inclined with respect to the circumferential and axialdirections of the mold, and the inner cylindrical shape may be the sameas the outer cylindrical shape.

According to still another aspect of the present invention, there isprovided a molding including: a cylindrical body made from a syntheticresin mold having an outer peripheral surface and, a parting line whichis inclined with respect to the circumferential and axial directions andwhich is produced on the outer peripheral surface upon molding thecylindrical body.

According to another aspect of the present invention, there is provideda molding including: a cylindrical body, made from a synthetic resinmold, having an inner peripheral surface and, a parting line which isinclined with respect to the circumferential and axial directions andwhich is produced on said inner peripheral surface upon molding thecylindrical body.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in detail with reference to theaccompanying drawings, in which:

FIG. 1 is a perspective view of a molding die assembly which is used tomold a first movable lens barrel according to the present invention;

FIG. 2 is a perspective view of a molding die assembly shown in adisassembled state;

FIG. 3 is a perspective view of a first movable lens barrel produced bythe molding die assembly shown in FIGS. 1 and 2;

FIG. 4 is a developed view of the first movable lens barrel shown inFIG. 3;

FIG. 5 is a sectional view of an upper half of a zoom lens barrel whichis made of the first movable lens barrel shown in FIGS. 3 and 4, withrespect to an optical axis;

FIG. 6 is a perspective view of a cylindrical body which has a spiralparting line formed on an inner peripheral surface thereof; and,

FIG. 7 is an enlarged sectional view of a cylindrical body and a lightintercepting film which is deformed by an axially extending parting lineof a certain height, so that a clearance is produced between thecylindrical body and the light intercepting film.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As can be seen in FIG. 5, a zoom lens barrel 10, according to thepresent invention, is comprised of two movable lens groups, i.e., afirst movable lens group L1 and a second movable lens group L2. In thezoom lens barrel 10, the zooming operation is carried out by moving thefirst and second lens groups L1 and L2 along a predetermined loci, andthe focusing operation is carried out by moving only the first lensgroup L1 without moving the second lens group L2. For the zoomingoperation the second lens group L2 is moved by a driving mechanism (notshown).

A stationary block 11, secured to the camera body, is provided with astationary ring (outer annular member) 12 secured thereto by a knownsecuring means (not shown). The stationary ring 12 is provided with apredetermined width of an elongated gear fitting groove 13 which extendsin the optical axis direction. The stationary ring 12 is provided on thefront end thereof with an annular light intercepting film 17 whose frontend is oriented toward the inner periphery. The light intercepting film17 is flexible and comes into sliding contact with the outer peripheralsurface of a first movable lens barrel 16 (cylindrical mold) which isinserted in the inner periphery of the stationary ring 12 to rotate andmove in the optical axis direction to optically intercept light in thegap between the stationary ring 12 and the first movable lens barrel 16.

The stationary ring 12 rotatably supports a shaft 50a of an elongatedrotation transmitting gear 50 which is inserted in the gear fittinggroove 13. The length of the transmitting gear 50 corresponds to atleast the displacement of the first movable lens barrel 16 in theoptical axis direction. The stationary block 11 rotatably supports adrive pinion 51 through a shaft 35 so that the pinion 51 is in mesh withthe rear end of the transmitting gear 50 which is exposed outside fromthe stationary ring 12. The drive pinion 51 is rotated by a drive motor(not shown) provided in the camera body, so that the rotation of thedrive pinion is transmitted to the transmitting gear 50.

The first movable lens barrel 16 is provided, on the outer peripheralsurface of the rear end thereof, with a multiple thread (male screw) 22and an outer peripheral gear 23. The male screw 22 is engaged by amultiple thread (female screw) 12a provided on the inner peripheralsurface of the stationary ring 12. The outer peripheral gear 23 isprovided with a plurality of threads (one thread corresponds to a groupof teeth 23a parallel with the optical axis O) which are inclined in thesame direction as the threads of the male screw 22. Each thread of themale screw 22 is formed between the threads of the gear 23. The outerperipheral gear 23 is in mesh with the transmitting gear 50, and isformed in the circumferential direction within a range corresponding tothe angular displacement of the first movable lens barrel 16 about theoptical axis O. In the illustrated embodiment, the five threads of themale screw 22 are cut away within a predetermined range in thecircumferential direction of the first movable lens barrel 16, so thatthe outer peripheral gear 23, consisting of a group of parallel gearteeth 23a parallel with the optical axis O, is formed in the cut-awayportion. The teeth 23a of the outer peripheral gear 23 are continuouslyconnected in the circumferential direction of the first movable lensbarrel 16.

A second movable lens barrel 19 is rotatably fitted in the innerperipheral surface of the first movable lens barrel 16. The second lensbarrel 19 is provided, on the outer peripheral surface of the rear endthereof, with a plurality of engaging projections 19a that are spaced atan equi-angular distance. The engaging projections 19a are slidablyfitted in a spiral cam groove 16a formed in the inner peripheral surfaceof the first movable lens barrel 16.

The second movable lens barrel 19 is provided on the inner peripheralsurface thereof with an annular AF/AE unit 20 having shutter blades 20cat the rear end thereof. The AE/AF unit 20 is provided on the innerperipheral surface thereof with a female helicoid 20b which is engagedby a male helicoid 25a formed on the outer peripheral surface of a lenssupporting frame 25 to which the first lens group L1 is secured. TheAE/AF unit 20 has a drive pin 37 which is driven in an angle in thecircumferential direction in accordance with object distance data. Thedrive pin 37 is engaged by an association arm 38 which projects in theradial direction of the lens supporting frame 25. Consequently, the lenssupporting frame 25 (first lens group L1) is moved in the optical axisdirection O in accordance with the angular displacement of the drive pin37 and the lead of the helicoids 20b and 25a to thereby effect focusing.In addition, the AF/AE unit 20 opens and closes the shutter blades 20cin accordance with luminance data of an object to be photographed.

The second movable lens barrel 19 is provided on the inner peripheralsurface thereof with a linear movement guide ring 27 having a linearmovement guide rail 27a which is slidably inserted in a guide portionprovided between the second movable lens barrel 19 and the AF/AE unit20.

The linear movement guide ring 27 is provided on the rear end thereofwith an outer peripheral flange 27b which projects outward, and thefirst movable lens barrel 16 is provided on the rear end thereof with aninner peripheral flange 16b that projects inward. The linear movementguide ring 27 is provided on the rear end thereof with a linear movementguide plate 28 secured thereto by a screw (not shown), so that the innerperipheral flange 16b is disposed between the linear movement guide ring27 and the outer peripheral flange 27b. The linear movement guide plate28 has a plurality of engaging projections 28a that project in radialand outward directions. The engaging projections 28a are slidablyengaged in a linear movement guide groove 12b formed in the innerperipheral surface of the stationary ring 12 to restrict the relativerotation of the linear movement guide ring 27 with respect to thestationary ring 12.

With this arrangement, the first movable lens barrel 16 is movabletogether with the linear movement guide ring 27 and the linear movementguide plate 28 in the optical axis direction O; and is rotatablerelative to the linear movement guide ring 27 and the linear movementguide plate 28. The second movable lens barrel 19 is not rotatablerelative to the stationary ring 12 and is linearly movable in theoptical axis direction O. The second movable lens barrel 19 is linearlymoved in the optical axis direction O by engaging the engagingprojections 19a in the cam groove 16a of the first movable lens barrel16.

The lens supporting frame 36, which holds the second lens group L2, hasa guide pin (not shown) which is engaged in a predetermined profile ofthe cam groove formed in the inner peripheral surface of the firstmovable lens barrel 16. Consequently, the lens supporting frame 36(second lens group L2) is reciprocally moved in the optical axisdirection O while keeping a predetermined relationship between the firstlens group L1, during the rotation of the first movable lens barrel 16.Note that 26 in FIG. 5 designates the lens covering cylinder provided atthe front end of the second movable lens barrel 19.

The first movable lens barrel 16 and the molding process therefor,according to the present invention will now be discussed below.

When the first movable lens barrel 16 is molded using a conventionalmolding die assembly, if a parting line PL of certain height is producedon the outer peripheral surface to extend in a parallel direction withthe optical axis direction, the light intercepting member 17 is partlydeformed or deflected by the parting line PL, as shown in FIG. 7, sothat a gap is formed between the light intercepting member 17 and thefirst movable lens barrel 16. Since the parting line PL extends parallelwith the optical axis O, the gap caused by the deformation or deflectionof the light intercepting member 17 continuously extends in a directionparallel to the optical axis O. In this state, if light is made incidentupon the lens from the front, the light partly enters the lens throughthe gap, thus resulting in a less reliable photographing operation.

To solve this problem, according to the basic concept of the presentinvention, the parting line is spiral with respect to the optical axisO, so that direct light from the object side can be certainlyintercepted; and, in addition to the foregoing, not only light enteringin the spiral direction (lead direction) hardly becomes direct light, inview of the fact that the lens barrel is cylindrical, but also no orlittle light can reach the inside of the lens barrel since the gap isalso curved. Namely, according to the present invention, the firstmovable lens barrel 16 is made of synthetic resin and has a parting linePL which is formed on the portion of the outer peripheral surface 16cthereof (excluding the male screw 22 and the outer peripheral gear 23),as can be seen in FIG. 3. The parting line PL is produced by the moldingdie assembly 30, which will be discussed below, and is inclined withrespect to the circumferential and axial directions to exhibit a spiralor helical shape with respect to the optical axis O. Note that theparting line PL extends to a direction parallel to the direction ofteeth of the male screw 22.

The molding die assembly 30 is comprised of an outer die 9 which isadapted to form an outer peripheral surface 16c of the first movablelens barrel 16, and an inner die 40 which is adapted to form the innerperipheral surface 16d, the front end surface 16e and the rear endsurface 16f. The inner die 40 includes a die portion 40a which islocated in front of the outer die 9, a die portion 40b which is locatedat the back of the outer die 9, and a die portion (not shown) which islocated on the inner peripheral surface side of the outer die 9 todefine a predetermined gap between the same and the inner peripheralsurface of the outer die 9, when the inner die 40 is assembled with theouter die 9 in a predetermined state. The outer die 9 is in the form ofa cylinder whose inner diameter is identical to the outer diameter ofthe first movable lens barrel 16. The outer die 9 is comprised of foursplit die elements 31, 32, 33 and 34 which are split at an equi-angulardistance with respect to the optical axis O, so that the molded productcan be removed (first movable lens barrel 16).

The split die elements 31, 32, 33 and 34 are provided with abuttingsurfaces 31a, 32a, 33a, and 34a which come into contact with the innerdie 40 and can be split at separating surfaces 31b, 31c, 32b, 32c, 33b,33c, 34b and 34c which are inclined with respect to the circumferentialdirection and the optical axis direction O. The connecting surfaces ofthe separating surfaces 31b, 31c, 32b, 32c, 33b, 33c, 34b and 34cexhibit, at the inner peripheral side, a spiral shape inclined withrespect to the circumferential direction and the optical axis directionO. Consequently, the parting line PL which is formed on the outerperipheral surface 16c of the first movable lens barrel 16 molded by themolding die assembly 30 is spirally or helically curved with respect tothe circumferential and axial directions.

The first movable lens barrel 16 is produced using the molding dieassembly 30 as will now be described.

To begin with, the outer die 9 consisting of the split die elements 31,32, 33 and 34, assembled as shown in FIG. 1, and the inner die 40 areassembled in a predetermined state to define a molding cavity forforming the first movable lens barrel 16.

In this state, a synthetic resin material is introduced to the moldingcavity. When the synthetic resin has set, after a predetermined time haslapsed, the split die elements 31, 32, 33 and 34 of the outer die 9 aresplit at the separating surfaces 31b, 31c, 32b, 32c, 33b, 33c, 34b and34c, as shown in FIG. 2. After that, the first movable lens barrel 16 isremoved from the inner die 40. The first movable lens barrel 16 thusmolded has a spiral parting line PL, on the outer peripheral surfacethereof, that is curved with respect to the optical axis direction O andthe circumferential direction, as shown in FIG. 3. If the parting linePL has a certain height, direct light entering from the object side canbe effectively interrupted, since it spirally extends. Moreover, sincethe first movable lens barrel 16 is cylindrical, no or little directlight can enter in the lead direction. Furthermore, since a gap,produced due to the parting line around the first movable lens barreland the outer or inner ring associated therewith, is also curved alongthe parting line, no light tends to enter the lens barrel. consequently,a light intercepting member, used to optically interrupt that lightinside the gap produced by the parting line can be dispensed with. Thus,a good light intercepting effect can be achieved through the use of onlythe light intercepting member 17, rendering the use of a special lightintercepting member to not be required.

The operation of the zoom lens barrel 10 as constructed above will nowbe explained.

When the drive motor (not shown) is driven, the rotation of the drivemotor is transmitted, to the outer peripheral gear 23 of the firstmovable lens barrel 16, through the drive pinion 51 and the transmissiongear 5O. Consequently, the advance of the lens barrel takes placethrough the screw-engagement between the male screw 22 and the femalescrew 12a of the stationary ring 12.

When the first movable lens barrel 16 is rotated, the second movablelens barrel 19 having the projections 19a which are engaged in the camgroove 16a formed in the inner peripheral surface of the lens barrel 16,and the lens supporting frame 36 having the guide pin which is engagedin the cam groove of the lens barrel 16, are advanced in the opticalaxis direction O while keeping a predetermined relationship.Consequently, the first lens group L1 and the second lens group L2 arelinearly advanced in the optical axis direction O while changing thespatial distance therebetween to effect the zooming operation.

Upon completion of the zooming, the AF/AE unit 20 drives the drive pin37 in the circumferential direction by a predetermined angle inaccordance with object distance data to advance the first lens group L1in the optical axis direction to thereby perform the focusing. Also, theAF/AE unit 20 opens and closes the shutter blades 20c at a predeterminedtime in accordance with luminance data of an object to be photographed.

Although the above discussion has been directed to an embodiment inwhich the spiral parting line PL is formed on the outer peripheralsurface of the first movable lens barrel 16, the present invention isnot limited to the illustrated embodiment. For instance, it is possibleto form a spiral parting line PL on the inner peripheral surface of acylindrical mold 53, using an inner die 40 which is comprised of splitdie elements similar to the outer die 9, as shown in FIG. 6.

Consequently, a light intercepting member used to optically interruptthe gap produced by the parting line is not necessary. Thus, a goodlight interruption can be established between the cylindrical body andan annular member provided on the inner peripheral surface thereof bythe use of only the light intercepting member, rendering the use of aspecial light intercepting member to not be required.

As can be understood from the above discussion, according to the presentinvention, if a cylindrical mold is used for, for example, a lens barrelfor a zoom camera, there is no leakage of light through and between thecylindrical mold and an inner or outer ring located on the inner orouter peripheral surface of the cylindrical mold, when a lightintercepting member is provided, even without the provision of a speciallight intercepting member.

Although the invention has been described with reference to particularmeans, materials and embodiments, it is to be understood that theinvention is not limited to the particulars disclosed and extends to allequivalents within the scope of the claims.

What is claimed is:
 1. A molding comprising:a cylindrical lens barrel ofa camera having an outer peripheral surface; and a parting line, saidparting line formed on said outer peripheral surface of said cylindricallens barrel during molding of said cylindrical lens barrel, and saidparting line inclined with respect to circumferential and axialdirections of said cylindrical lens barrel, said cylindrical lens barrelbeing formed from a synthetic resin molding material.
 2. A moldingaccording to claim 1, said cylindrical lens barrel has a male screwformed on said outer peripheral surface, the male screw comprising aplurality of teeth, and said parting line extends in a directionparallel to said plurality of teeth.
 3. A molding comprising:a moldedcylindrical lens barrel of a camera having an inner peripheral surface;and a parting line formed during molding of said cylindrical lens barreland inclined with respect to circumferential and axial directions ofsaid cylindrical lens barrel and produced on said inner peripheralsurface said cylindrical lens barrel, being formed from a syntheticresin molding material.
 4. A molding formed by a plurality of dies,comprising:a cylindrical body made of a synthetic resin molding materialhaving outer and inner peripheral surfaces; and a plurality of partinglines, equal to a number of said plurality of dies, on only one of saidouter and inner peripheral surfaces, said plurality of parting linesbeing inclined with respect to circumferential and axial directions ofsaid cylindrical body.
 5. The molding of claim 4, wherein saidcylindrical body is a lens barrel.
 6. The molding of claim 4, whereinsaid plurality of parting lines extend parallel with each other.
 7. Themolding of claim 6, wherein said plurality of parting lines are offsetfrom each other along said circumferential direction.
 8. The molding ofclaim 4, said cylindrical body having a circular male screw, the malescrew comprising a plurality of helicoidal teeth, and said at least twoparting lines extend in a direction parallel to said plurality of teeth.